A probe into a collision between a ferry and a fishing boat that left a teenage fisherman lost at sea has got under way.

Rescue crews have called off the search for the 16-year-old, who went missing after his boat and the Scottish Viking passenger ferry collided in the North Sea.

The teenager, believed to be from North Shields, was on board the Homeland vessel with his brother when it made contact with the other boat five miles (8km) off the coast of St Abbs in Eyemouth, Berwickshire, on Thursday night. His 20-year-old brother - the fishing boat's skipper - was pulled from the water by another vessel.

Four lifeboat crews and up to 20 fishing vessels scanned an area of just under five square miles on Friday.

The rescuers were stood down on Friday night, but the Coastguard said local fishing boats may continue searching for the missing teenager.

Fred Caygill, of the Maritime and Coastguard Agency (MCA), said: "The survivability period for someone in the water has passed. Different factors affect different people's chances of survival, but it has been a long time. Some lifejackets were found at the scene but it's not known if the missing person was wearing a lifejacket."

The Homeland, registration number BH120, operates from North Shields in Tyneside.

The passenger ferry is run by Norfolkline, part of DFDS Seaways, which operates services between Rosyth, Scotland, and Zeebrugge in Belgium.

DFDS Seaways said the ferry was chartered by Norfolkline from Italian firm Visentini. Visentini said an investigation into the accident would be carried out.

A DFDS Seaways spokesman said the company was "deeply concerned" about the accident. The Marine Accident Investigation Branch (MAIB) has also launched a probe.